\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{circuitikz}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\ctikzset{bipoles/length=1cm}
\begin{document}
\small
\begin{circuitikz}[>=latex, scale=1.0,european]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw (0,0)--(3,0) node [right]{$b$};
  \draw (0,5)--(1.5,5) to [R=\qty{10}{k\ohm}] (1.5,2.5) to [R=\qty{10}{k\ohm}, *-*] (1.5, 0);
  \draw (1.5,2.5)--(3,2.5) node [right]{$a$};
  \draw [<->](0,0+.1)--node [fill=white] {\qty{50}{V}} (0,5-.1);
  \draw [fill=white](0,0) circle (2pt);
  \draw [fill=white](0,5) circle (2pt);
  \draw [fill=white](3,0) circle (2pt);
  \draw [fill=white](3,2.5) circle (2pt);
\end{circuitikz}
\end{document}